Catalytic reduction of NOx with high activity catalysts

Abstract

Methods and systems for selective catalytic reduction of NOx with an activated-carbon-supported metal catalyst at an operating temperature of between about between about 500° C. and about 750° C. An exhaust stream including NOx is introduced to a catalytic reactor having the activated-carbon-supported metal catalyst for NOx reduction of at least 90%. A second catalyst reactor can be provided downstream to remove or convert nitrous oxide as desired.

The invention claimed is: 
     
       1. A method for selective catalytic reduction of NOx comprising:
 providing an exhaust stream from a combustion operation, the exhaust stream containing an amount of NOx; 
 introducing at least a portion of the exhaust stream to a catalytic reactor comprising at least one activated-carbon-supported metal catalyst, the operating temperature of the catalytic reactor being between about 500° C. and about 750° C. to reduce the amount of NOx in the exhaust stream; and 
 directing the NOx-reduced exhaust stream from the catalytic reactor. 
 
     
     
       2. The method of  claim 1 , wherein the exhaust stream is free of an effective amount of fluid reductant. 
     
     
       3. The method of  claim 1 , wherein the exhaust stream is provided from at least one refinery component selected from the group consisting of a combustion furnace, a boiler, a heater turbine, and a fluid catalytic cracking unit. 
     
     
       4. The method of  claim 3 , wherein the catalytic reactor is located near a flue of the at least one refinery component to maintain the catalytic reactor between about 500° C. and 750° C. 
     
     
       5. The method of  claim 1 , wherein the operating temperature of the catalytic reactor is maintained between about 500 ° C. and about 750° C. by heating the exhaust stream. 
     
     
       6. The method of  claim 1 , wherein the exhaust stream includes between about 1% and about 20% oxygen and between about 1% and about 10% water. 
     
     
       7. The method of  claim 1 , wherein the exhaust stream has a gaseous hourly space velocity of at least about 5000 cc per hour. 
     
     
       8. The method of  claim 1 , wherein the exhaust stream has a gaseous hourly space velocity between about 30K cc per hour and about 120K cc per hour. 
     
     
       9. The method of  claim 1 , wherein the activated-carbon-supported metal catalyst includes a transition metal. 
     
     
       10. The method of  claim 1 , wherein the activated-carbon-supported metal catalyst includes a noble metal. 
     
     
       11. The method of  claim 1 , wherein the activated-carbon-supported metal catalyst includes a Group 10 element. 
     
     
       12. The method of  claim 1 , wherein the activated-carbon-supported metal catalyst includes one of the group consisting of platinum, ruthenium, cobalt, rhenium, iron, nickel, palladium, and copper. 
     
     
       13. The method of  claim 1 , wherein the amount of NOx is reduced by at least 90%. 
     
     
       14. The method of  claim 1 , further comprising reducing an amount of N2O in the NOx-reduced exhaust stream. 
     
     
       15. The method of  claim 14 , wherein reducing the amount of N2O comprises introducing the at least a portion of the NOx-reduced exhaust stream to a second catalyst. 
     
     
       16. The method of  claim 15 , wherein a fluid reductant stream including ammonia is introduced into the NOx-reduced exhaust stream upstream of the second catalyst. 
     
     
       17. The method of  claim 15 , wherein the catalytic reactor includes a vessel and the second catalyst is within the vessel of the catalytic reactor. 
     
     
       18. The method of  claim 15 , wherein the second catalyst is in a second catalytic reactor, the second catalytic reactor located downstream of the catalytic reactor. 
     
     
       19. The method of  claim 15 , wherein the second catalyst comprises a zeolite loaded with a metal. 
     
     
       20. The method of  claim 15 , wherein the second catalyst comprises Cu loaded on ZSM-5. 
     
     
       21. The method of  claim 15 , wherein the operating temperature of the second catalyst is between about 200° C. and about 250° C. 
     
     
       22. A system for selective catalytic reduction of NOx comprising:
 a conduit in fluid communication with a source of an exhaust stream from a combustion operation, the exhaust stream containing an amount of NOx; 
 a heat exchanger operatively coupled to the conduit to heat the exhaust stream to maintain the catalytic reactor at between about 500° C. and about 750° C.; 
 a catalytic reactor in fluid communication with the conduit, the catalytic reactor comprising at least one activated-carbon-supported metal catalyst, the operating temperature of the catalytic reactor being between about 500° C. and about 750° C. to reduce the amount of NOx in the exhaust stream; and 
 an outlet in fluid communication with the catalytic reactor to direct the NOx reduced exhaust stream from the catalytic reactor. 
 
     
     
       23. The system of  claim 22 , wherein the source of the exhaust stream is a refinery component selected from the group consisting of a combustion furnace, a boiler, a heater turbine, and a fluid catalytic cracking unit. 
     
     
       24. The system of  claim 22 , wherein the at least one activated-carbon-supported metal catalyst includes a noble metal selected from platinum, ruthenium, rhenium, or palladium. 
     
     
       25. A system for selective catalytic reduction of NOx comprising:
 a conduit in fluid communication with a source of an exhaust stream from a combustion operation, the exhaust stream containing an amount of NOx; 
 a catalytic reactor in fluid communication with the conduit, the catalytic reactor comprising at least one activated-carbon-supported noble metal catalyst, the operating temperature of the catalytic reactor being between about 500° C. and about 750° C. to reduce the amount of NOx in the exhaust stream; and 
 an outlet in fluid communication with the catalytic reactor to direct the NOx reduced exhaust stream from the catalytic reactor. 
 
     
     
       26. A system for selective catalytic reduction of NOx comprising:
 a conduit in fluid communication with a source of an exhaust stream from a combustion operation, the exhaust stream containing an amount of NOx; 
 a catalytic reactor in fluid communication with the conduit, the catalytic reactor comprising at least one activated-carbon-supported metal catalyst, the operating temperature of the catalytic reactor being between about 500° C. and about 750° C. to reduce the amount of NOx in the exhaust stream; and 
 an outlet in fluid communication with the catalytic reactor to direct the NOx reduced exhaust stream from the catalytic reactor; 
 a second catalyst in fluid communication with the outlet and operatively configured to reduce an amount of nitrous oxide in the NOx-reduced exhaust stream. 
 
     
     
       27. The system of  claim 26 , further comprising a source of a fluid reductant stream including ammonia operatively configured to introduce the reductant stream upstream from the second catalyst. 
     
     
       28. The system of  claim 27 , wherein the catalytic reactor includes a vessel and the second catalyst is within the vessel of the catalytic reactor. 
     
     
       29. The system of  claim 27 , wherein the second catalyst is in a second catalytic reactor, the second catalytic reactor located downstream from the catalytic rector. 
     
     
       30. The system of  claim 26 , wherein the second catalyst comprises a zeolite loaded with a metal. 
     
     
       31. The system of  claim 26 , wherein the second catalyst comprises Cu loaded on ZSM-5. 
     
     
       32. The system of  claim 26 , wherein the second catalyst is located downstream from the catalytic reactor to maintain the operating temperature of the second catalyst is between about 200° C. and about 250° C. 
     
     
       33. The system of  claim 26 , further comprising a heat exchanger operatively coupled to heat the NOx-reduced exhaust stream to maintain the second catalyst at between about 200° C. and about 250° C.